Patent GB-1223710-A (GB)
Title: Improvements in or relating to lenses for electromagnetic wave energy
Inventor: BUCHSBAUM SOLOMON JAN
IPC: G02F1/295
Filed: 1968-10-24
Abstract: 1,223,710. Focusing light guide. WESTERN ELECTRIC CO. Inc. 24 Oct., 1968 [25 Oct. 1967], No. 50518/68. Heading H4F. [Also in Division G2] A lens for a light beam comprises a conduit 11, Fig. 1, having transverse cross-sectioned dimensions many times greater than the wavelength of the light beam, the conduit being filled with a transparent liquid 13 containing particles 20 capable of scattering the light beam coherently in the forward direction, either the liquid or the particles responding to an electric field (or magnetic field) to produce a lens-like distribution of the particles in the liquid. In Fig. 1, the conduit comprises a fused dielectric material e.g. glass, and is filled with water which supports colloided particles e.g. glass particles, having dimensions that are at least two orders of magnitude smaller than the wavelength of the visible light transmitted e.g. a laser beam. The particles scatter light coherently in the forward direction i.e. they absorb and re-radiate most of the light coherently. Electrode rings 14 and 15 are connected to a D.C. (or A.C.), voltage source 19 as shown so that an essentially axial electric field is produced, its intensity being smallest on the axis of the conduit. The glass particles 20 have a lower low-frequency dielectric constant than the water and therefore migrate out of the regions of high electric field intensity and have their greatest concentration near the axis of the conduit. Since the glass particles refractive index is 1À5 as compared to 1À33 for water, the resulting index of refraction gradient is that for a converging lens. The entire assembly is equivalent to a series of closely spaced, weakly focusing, radially symmetrical lenses. To direct the light beam around a bend the lens units are regular spaced around the bend, alternatively the applied electric (or magnetic) field is distorted so that the greatest concentration of material with the high refractive index is established on the inside of the bend Fig. 2 (not shown), the electrodes on the outside of the bend being displaced toward the centre of the conduit. In addition prisms or mirrors, may be utilized. In a further embodiment, Fig. 3, liquid 33 may comprise water or a freon such as polyfluorinated heptane (C 7 F 16 ), the particles being diamagnetic atoms e.g. benzene atoms. Where a lens-like distribution of particles is to be achieved to provide focusing action, electromagnets 34 comprising annuli 35 of soft iron material girdle the fused dielectric 32 at regular spacings. Field coil 36 supplies flux through the annuli 35. Permanent magnets may be used. Focusing sections such as shown in Fig. 3 are periodically spaced along the entire transmission path. To obtain stronger focusing effect than that of Fig. 3 paramagnetic atoms may be utilized that migrate towards regions of high magnetic field. To avoid the resulting defocusing action (the paramagnetic solute has a higher refractive index than the solvent) strong focusing is employed with cylindrical lens-like elements Fig. 4A (not shown), focusing alternating with defocusing with relative spacing such that a net focusing action results. In the embodiment of Fig. 4A (not shown) focusing is effected in one coordinate while defocusing is occurring in the orthogonal co-ordinate, and vice versa, by arranging the magnetic sections to alternate axially along the conduit so that a line drawn through successive north poles would trace a helix and a line drawn through successive south poles would trace a helix. The paramagnetic atoms may comprise cobalt dichloride (CoCl 2 ) or copper sulphate (CuSO 4 ) in water. In a further embodiment Figs. 5A and 5B (not shown) the dielectric conduit is surrounded by a soft iron pipe (serving as a magnetic flux return path) having on its interior surface signaling magnetic ribs. A second technique for employing paramagnetic materials to produce a net focusing action, combines a paramagnetic liquid and a non-magnetic solute of higher refractive in a magnetic structure like that of Fig. 3. Colloidal suspensions of lithium niobate (LiNbO 3 ) particles in C 7 F 16  may be utilized in an electric structure like that of Fig. 1, the particles being ferroelectric and having permanent electric dipole movements. In operation the lithium niobate particles migrate into the regions of highest electric field. Solutions of dielectric and paraelectric atomic particles may be utilized and examples are given in the Specification.